Spencer Graves
2022-Jun-25 13:13 UTC
[Rd] as.Date (and strptime?) does not recognize " " as a blank
Hi, Maxim et al.: On 6/25/22 6:10 AM, Maxim Nazarov wrote:> Hello, > >> When is a space not a space? > I guess the answer is when it is a non-breaking one?.. > > We can observe: > > charToRaw(textutils::HTMLdecode(" ")) > [1] c2 a0 > > charToRaw(" ") > [1] 20 > So one can argue that everything works correctly - `textutils` function converts HTML's non-breaking space ' ' into R's non-breaking space '\xa0', while %e format of as.Date expects a 'normal' space. > But this is obviously not user-friendly especially since both symbols are displayed the same way on the console. > So your options might be to either: > * manually change all 'weird' spaces into normal ones with something like gsub("\\h", " ", ..., perl = TRUE) - for the list of other weird spaces see https://www.pcre.org/original/doc/html/pcrepattern.html#genericchartypes > * persuade textutils author to change into a normal space (they seem to be working with a simple lookup table - https://github.com/enricoschumann/textutils/blob/b813c7bd4b55daef5fa7612e3fbfe82962711940/R/char_refs.R#L1465-L1466) > * persuade R-Core (or submit a PR) to relax expectations of as.Date/strptime >Thanks for the reply. Since "this is obviously not user-friendly", as you noted, I felt a need to bring it to the attention of this group, and let them decide what if anything they would want to do about it. In any event, I found a fix for my immediate problem. It's not as elegant as yours, but it works. Best Wishes, Spencer> Kind regards, > Maxim Nazarov > > ----- On Jun 25, 2022, at 8:37 AM, Spencer Graves spencer.graves at prodsyse.com wrote: > >> Hello, All: >> >> >> When is a space not a space? >> >> >> Consider the following: >> >> >>> (pblmDate <- textutils::HTMLdecode(" 2 Mar 2018")) >> [1] " 2 Mar 2018" >>> as.Date(pblmDate, format='%e %b %Y') >> [1] NA >>> as.Date(' 2 Mar 2018', format='%e %b %Y') >> [1] "2018-03-02" >> >> >> Is this a feature or a bug? >> >> >> I can work around it, now that I know what it is, but it took me a >> few hours to diagnose. >> >> >> Thanks, >> Spencer Graves >> >> >> p.s. I got this from scraping a website with code that had worked for >> me roughly 20 months ago. I suspect that in the interim, someone >> probably replaced ' 2 Mar 2018' with " 2 Mar 2018". >> >> ______________________________________________ >> R-devel at r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel
Prof Brian Ripley
2022-Jul-07 11:59 UTC
[Rd] as.Date (and strptime?) does not recognize " " as a blank
There is some misunderstanding here. The space is part of the format
specified by SG to as.Date(), which passes it to strptime(). So SG asked
to match a space and complained that a different character is not matched!
Reading the documentation of strptime shows
?%n? Newline on output, arbitrary whitespace on input.
?%t? Tab on output, arbitrary whitespace on input.
so one might hope that one could use those to specify whitespace instead
of ASCII space in the format. But unfortunately whether a Unicode
no-break space (U+00A0) is whitespace is a matter of opinion -- for
example the PCRE author changed his a few years back.
We don't have a reproducible example, but my attempt at reproduction
suggests that U+00A0 is not regarded as whitespace on the system I used.
We know this to be platform-specific (it uses the C function
iswspace): glibc does not regard this as whitespace and the replacement
functions used by R on macOS and Windows have followed suit.
In short, ASCII space matches only itself, and the interpretation of
'blank' (in regexps) or 'whitespace' (in strptime or regexps) is
platform-specific and liable to change.
On 25/06/2022 14:13, Spencer Graves wrote:> Hi, Maxim et al.:
>
>
> On 6/25/22 6:10 AM, Maxim Nazarov wrote:
>> Hello,
>>
>>> When is a space not a space?
>> I guess the answer is when it is a non-breaking one?..
>>
>> We can observe:
>> ? > charToRaw(textutils::HTMLdecode(" "))
>> ? [1] c2 a0
>> ? > charToRaw(" ")
>> ? [1] 20
>> So one can argue that everything works correctly - `textutils`
>> function converts HTML's non-breaking space ' '
into R's
>> non-breaking space '\xa0', while %e format of as.Date expects a
>> 'normal' space.
>> But this is obviously not user-friendly especially since both symbols
>> are displayed the same way on the console.
>> So your options might be to either:
>> ? * manually change all 'weird' spaces into normal ones with
something
>> like gsub("\\h", " ", ..., perl = TRUE) - for the
list of other weird
>> spaces see
>>
https://www.pcre.org/original/doc/html/pcrepattern.html#genericchartypes
>> ? * persuade textutils author to change into a normal space
>> (they seem to be working with a simple lookup table -
>>
https://github.com/enricoschumann/textutils/blob/b813c7bd4b55daef5fa7612e3fbfe82962711940/R/char_refs.R#L1465-L1466)
>>
>> ? * persuade R-Core (or submit a PR) to relax expectations of
>> as.Date/strptime
>>
>
> ????? Thanks for the reply.? Since "this is obviously not
> user-friendly", as you noted, I felt a need to bring it to the
attention
> of this group, and let them decide what if anything they would want to
> do about it.
>
>
> ????? In any event, I found a fix for my immediate problem.? It's not
> as elegant as yours, but it works.
>
> ????? Best Wishes,
> ????? Spencer
>
>
>
>
>> Kind regards,
>> Maxim Nazarov
>>
>> ----- On Jun 25, 2022, at 8:37 AM, Spencer Graves
>> spencer.graves at prodsyse.com wrote:
>>
>>> Hello, All:
>>>
>>>
>>> ????? When is a space not a space?
>>>
>>>
>>> ????? Consider the following:
>>>
>>>
>>>> (pblmDate <- textutils::HTMLdecode(" 2 Mar
2018"))
>>> [1] " 2 Mar 2018"
>>>> as.Date(pblmDate, format='%e %b %Y')
>>> [1] NA
>>>> as.Date(' 2 Mar 2018', format='%e %b %Y')
>>> [1] "2018-03-02"
>>>
>>>
>>> ????? Is this a feature or a bug?
>>>
>>>
>>> ????? I can work around it, now that I know what it is, but it took
me a
>>> few hours to diagnose.
>>>
>>>
>>> ????? Thanks,
>>> ????? Spencer Graves
>>>
>>>
>>> p.s.? I got this from scraping a website with code that had worked
for
>>> me roughly 20 months ago.? I suspect that in the interim, someone
>>> probably replaced ' 2 Mar 2018' with " 2 Mar
2018".
>>>
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford